MTV News first interviewed Justin Bieber in September of 2009, when the pint-size pop singer was on the cusp of breaking beyond his core audience into mainstream pop stardom. Then 15 years old and relatively new to the national media spotlight, Bieber wasn't nervous so much as generally tentative, a bit clipped and repetitive in his answers.

When Bieber walked into the MTV Newsroom earlier this month to promote his

3-D flick, "Never Say Never," the difference in his on-camera demeanor couldn't have been more different: He projected a breezy confidence, at times humorous or eye-on-the-prize focused, and was engaging throughout.

That Bieber has truly matured — not just as an artist, but as a person — isn't apparent only to those who occasionally cross his path. Jon M. Chu, who directed "Never

Say Never" and began working with the singer in August, has noticed the change as well.

"With the movie and going to the Grammys and being respected on so many different levels beyond just his own fanbase, he's really growing up and learning how to interact with people," Chu said.

The director said he noted a great difference in the young star's disposition following the completion of his seven-month, 86-show tour.

"He's just had time to rest," said Chu, who started shooting "Never Say Never" as Bieber was in the midst of that nonstop North American tour. At first, Bieber was standoffish. Only gradually did the two establish a close creative partnership.

"Half of it was just me gaining trust with him because I was in his face with a camera," Chu said. "It was very much like 'Almost Famous,' where I was just on the bus and he didn't really want me there. Once we got past that, we were fine."